Polycarboxylate polymers, especially acrylic and maleic polymers, are well-known ingredients of detergent compositions and provide various benefits. They are used, for example, as antiredeposition and antiincrustation agents; for detergency building, especially in conjunction with water-insoluble aluminosilicate builders; and for the structuring of detergent powders.
Published documents describing the use of acrylic and maleic polymers in detergent compositions include GB 1 460 893 (Unilever) which discloses polyacrylates; EP 25 551B (BASF) which discloses acrylic/maleic copolymers; and EP 124 913B (Procter & Gamble) which discloses detergent compositions containing combinations of polyacrylate and acrylic/maleic copolymer.
Although various polycarboxylate polymers have been disclosed in the literature as detergent ingredients, only polyacrylates and acrylate/maleate copolymers have found widespread use in commercial detergent products. These polymers, however, are not biodegradable.
The present invention is based on the discovery that the incorporation of ketone units into the backbone of such carboxylic polymers results in improved biodegradability without loss of detergency building (calcium binding) capacity. These units may be introduced into the polymer by means of the compound 2,2'-diphenyl-4-methylene-1,3-dioxolane or a related compound. The polymerisation reaction is controllable, may be readily carried out at atmospheric pressure, neat or in aqueous or non-aqueous solution, to give high yields of biodegradable polymers of good calcium binding capacity.
U.S. Pat. Nos. 3 761 412 and 3,764,586 (Lancelot et al/FMC Corporation) disclose poly-beta-keto acids, useful as detergency builders, which are copolymers of carbon monoxide gas and maleic anhydride. The polymerisation reaction requires high pressure and the presence of an organic solvent, and yields are poor (typically 12-24%).
EP 281 139A (Mitsubishi) discloses terpolymers of ethylene (or other lower olefin), maleic anhydride and carbon monoxide which are useful as biodegradable detergency builders. The presence of the olefin facilitates the polymerisation process and improves yield, but the polymerisation process still requires high pressure and high temperature, and is not consistently reproducible.
A different approach is described in JP 02 073 811A (Hitachi) which discloses a copolymer of acrylic acid and 2-cyclohexen-1-one, useful as a detergency builder.
2,2'-diphenyl-4-methylene-1,3-dioxolane and its homopolymers were first described by Y Hiraguri and T Endo, J Am Chem Soc 1987, 109, 3779-3780. Further studies involving related compounds, and copolymers with non-carboxylic vinyl monomers, are described in three papers by the same authors in J Polymer Science: Part A, Polymer Chem 1989, 27, 2135-3138 and 4403-4411, and Part C, Polymer Lett 1989, 27, 1-4. However, there is no disclosure of copolymerisation of this material with carboxylic monomers.